function getCookie(c_name) {
    if (!c_name) {

        //核心
        return document.cookie;
    }

    if (document.cookie.length > 0) {
        c_start = document.cookie.indexOf(c_name + "=")
        if (c_start != -1) {
            c_start = c_start + c_name.length + 1
            c_end = document.cookie.indexOf(";", c_start)
            if (c_end == -1) c_end = document.cookie.length
            return unescape(document.cookie.substring(c_start, c_end))
        }
    }
    return ""
}

function setCookie(name, value, time) {
    var exp = new Date();
    exp.setTime(exp.getTime() + time * 1000);
    document.cookie = name + "=" + escape(value) + ";expires=" + exp.toGMTString()//+";path=/";
}


function checkCookie() {
    username = getCookie('username')
    if (username != null && username != "") {
        alert('Welcome again ' + username + '!')
    } else {
        username = prompt('Please enter your name:', "")
        if (username != null && username != "") {
            setCookie('username', username, 365)
        }
    }
}